The present invention relates to a gear train mechanism stop device which is used in a timepiece comprising clock signal producing means; a rotational movement source for generating a given rotational movement in response to a clock signal generated from the clock signal producing means; time indication hand means having at least hour and minute hands; and a gear train mechanism for transmitting the rotational movement from the rotational movement source to the time indication hand means so as to make the time indication hand means move in a given movement, and which is selectively engaged with a specified gear in the gear train mechanism so as to stop rotation of the specified gear.
In a gear train mechanism stop device of a timepiece such as an analog wristwatch of a battery-powered type, a crown normally serves as an operation member of the device. When the crown is moved from a pushed-in position to a drawn-out position, an electronic circuit constituting a clock signal producing means is reset so as to be inhibitated a producing of a clock signal, and a specified gear in a gear train mechanism is stopped, thereby stopping rotational movement transmission from a rotational movement source to a time indication hand means. When the crown at the drawn-out position is rotated clockwise or counterclockwise, hour and minute hands of the time indication hand means can be moved in order to correct time.
In the conventional timepiece gear train mechanism stop device, a rockable member is coupled to an internally extending portion of the crown so as to be rocked between first and second positions upon movement of the crown between the pushed-in and drawn-out positions. The rockable member is coupled to a rotational type engaging member. When the rockable member rotates from the first position to the second position, the engaging member rotates to its engaged position at which the distal end of the engaging member is engaged with the tooth of the specified gear in the gear train mechanism from the radial direction of the corresponding gear. When the rockable member rotates from the second position to the first position, the engaging member rotates to its disengaged position at which the distal end of the engaging member is separated from the tooth or the specified gear in the gear train mechanism in the radial direction of the corresponding gear.
In the conventional timepiece gear train mechanism stop device, not only a pivotal central shaft of the rotational type engaging member, but also a relatively large space in the horizontal direction is necessary in order to rotate the engaging member. Therefore, the number of parts in the timepiece and manufacturing costs are increased, and assembly becomes complex. In addition, it is difficult to reduce the whole size of the timepiece. Furthermore, since the engaging member is engaged with the tooth of the specified gear in the gear train mechanism from the radial direction thereof, a relatively large force is applied to a bearing for the specified gear engaged with the engaging member from the radial direction of the specified gear, and the bearing thus wears down easily. In addition, the tooth of the specified gear engaged with the engaging member also wears down easily.
Another timepiece gear train mechanism stop mechanism has been shown in U.S. Pat. No. 3,691,753. In this patent, a cam is concentrically fixed to one gear in a gear train mechanism. When a rotational type engaging member is engaged with the cam from the radial direction of the gear, rotation of the gear is stopped.
The gear train mechanism stop device shown in U.S. Pat. No. 3,691,753 can prevent the tooth of the gear in the gear train mechanism from being worn down, since the rotational type engaging member is not engaged with the tooth of the gear from the radial direction of the gear. However, the other problems of the conventional device cannot be resolved.